Process for treating a hydrocarbon mixture which is contaminated by small amounts oforganic fluorine compounds



Patented Oct. 7, 1947 PROCESS FOR TREATING A HYDRQCARBON MIXTURE WHICH-IS CONTAMINATED BY SMALL AMOUNTS F ORGANI/CFLUORINE .comrourms Carl B.Linn, Riverside, Ill; assignor Universal 0i] Products Company, Chicago,111., a corporation of Delaware No Drawing. Application September 28,1945, Serial No. 619.252

16 Claims. (01. 2605-676) This invention relates to a process fortreating a hydrocarbon or hydrocarbon mixture which is contaminated bysmall amounts of organic fluorine compounds to remove fluorinetherefrom.

More specifically, it relates to the treatment of hydrocarbons producedsynthetically in the presence of an active fluoride catalyst to removesmall amounts of organically combined fluorine present in compoundsadmixed with the hydrocarbon or hydrocarbon mixture.

The invention is particularly adapted to the a treatment of hydrocarbonsproduced by the alkvlation of isoparafllnic hydrocarbons with oleflnichydrocarbons or with alkyl fluorides using active fluoride catalystsincluding hydrogen fluoride or fluoride mixtures comprising essentiallyhydrogen fluoride and boron fluoride. The process is also applicable tothe removal of alkyl fluorides from propane and butane fractions. saidfractions being recovered from the gaseousproducts discharged from analkylation plant in which isobutane is alkylated by olefins present in apropane-propylene or butane-butylene fraction.

An obiect of this invention is to defluorinate a hydrocarbon orhydrocarbon mixture contaminated by relatively small amounts of organicfluorine compounds, part cularly alkyl fluor des.

Another obiect of this invention is to dehydrofluorinate an' isoparafllnalkylation product formed in the presence of an active fluoridecatalyst.

A further obiect of this invention is to remove alkyl fluorides fromhydrocarbon conversion products formed in the presence of an activefluoride catalyst.

A still further ob ect of this invention is to remove alkyl fluoridesfrom a fraction of normally gaseous parafflnic hydrocarbons recoveredfrom the produc s formed in the a kvlation of isohutane h olefinspresent in a C -C hydrocarbon fraction.

Another ob ect 01' this invention is to remove eth l fluor de from apropane fraction recovered from the products formed in the alkylation ofis butane in the presence of hydrogen fluoride with a propa e-propvlenefraction containing a relatively small amount of ethylene.

One specific embodiment of the present invention comprises a process fortreating hydroc rbon material contain ng as an impurity a relativelysmall percentage of organically combined fluorine to remove fluorinetherefrom which comprises contactin said material with fluosulfonic acidat dehydrofluoriniting conditions of temperature 1 2 and pressure, andrecovering the treated hydrocarbon material.

Another embodiment of the present invention comprises a process fortreating hydrocarbons recovered from an alkylation process in which anisoparaflin is alkylated with an olefin in the Qpresence of an activefluoride catalyst, by treating said hydrocarbons with fluosulfon c acidat dehydrofluorinating conditions of temperature,

pressure and time, and recovering the treated hydrocarbons.

The alkylation of branched chain paraflinic hydrocarbons such asisobutane and isopentene with. oleflnic hydrocarbons, particularly theoleflnic hydrocarbons present in cracked gases, produces saturatedliquid hydrocarbons utilizable as constituents of gasoline of highantiknock value. By this means relatively low boiling isoparafflnichydrocarbons are alkylated with low boiling olefins and therebyconverted into materials of higher boiling po nt and high antiknockvalues. The higher boiling hydrocarbons so formed from low boilingisoparaffins and olefins in the presence of an active fluoride catalvstincluding hydrogen fluoride or mixtures of hydrogen fluoride and boronfluor de, frequently contain small amounts of organic fluorine compoundswhich are not readily removable by washing with caustic and water or byfractional distillation.

These contaminating fluorine compounds which are thus present inalkylation hydrocarbon mixtures are frequently due to the interaction ofhydrogen fluoride with olefins to form alkyl fluorides. Some alkylfluorides are more stable than others in the presence of active fluoridecatalysts. Thus, ethyl fluoride is more stable than some of the highermolecular weight alkyl fluorides in an alkylat on reaction mixture andis not converted completely into paraflinic alkvlation products but admxes with the hydrocarbon products. Some higher boiling alk l fluoridesand other organic fluorine compounds ma also remain in hydrocarbonalkvlation products. Because of its h gh stability, boiling 'point, andthe fact that it forms w th propane an azeotrope boiling at -47 C.,ethyl fluoride is found in the by the addition of hydrogen fluoride tothis olefin of lowestmolecular weight.

Boron fluoride assists hydrogen fluoride in catalyzing the alkylation ofan isoparaflln by ethylene and higher oleflns, but in these cases thealkylation product also contains small quantities of organic fluoridesas do those formed in the presence of hydrogen fluoride from anisoparaflin and an olefin of higher molecular weight than ethylene.

Although the fluorine content of the hydrocarbon product ofgasolineboiling range resulting from an alkylation treatment is rarelyvery high,

the presence of fluorine is undesirable both fromabout 0.001%, or less,by Weight of fluorine from a contaminated matc.ial containing 1.2%fluorine present as ethyl fluoride. These results are remarkableandunpredictable because I have also ing agent such as lead tetraethyl isadded thereto.

not alkylated during the alkylation treatment of an isoparaflin witholeflns present in a C3 or a' C4 hydrocarbon fraction are recovered fromalkylation products and marketed as bottled gas for use as domesticfuels and for various industrial uses. Such recovered propane and normalbutane fractions are sometimes contaminated by ethyl fluoride and otherorganic fluorine compounds formed incidentally in the alkylationtreatment and it is desirable that these propane and butane fractions befreed from fluorine compounds before being so utilized as fuel. I

It is much more diflicult to dehydrofluorinate ethyl fluoride than theother alkyl fluorides which may be encountered in products of thehydrogen fluoride alkylation process. It has been observed thatalkylation plants which charge a propane-propylene feed stock to thealkylation reactor produce ethyl fluoride from the ethylene whichsometimes contaminates the C3 feed stock. This ethyl fluoride tends togo through the plant unchanged and finally appears in the propanefraction recovered from the eilluent gases. The methods used heretoforefor removing organic fluorine compounds from alk'ylate, such as passagethrough heated contactors containing bauxite or aluminum, do not causesufficient dehydrofluorination of ethyl fluoride and consequently areineffective for producing a propane fraction substantially free fromfluorine. My process, however, does defluorinate not only the gasolineboiling range material but also propane and butane and makes it possibleto produce substantially fluorine-free propane and butane fractions.

As indicated above, ethyl fluoride is more stable than the higher alkylfluorides encountered in the products of the hydrogen fluoridealkylation process. Possibly one reason for this difierence in stabilityof the alkyl fluorides is the fact that ethyl fluoride is a primaryalkyl fluoride, while the alkyl fluorides produced from propylene andhigher oleflns are either secondary or tertiary alkyl fluorides. I havefound that when propane which is contaminated by small amounts of ethylfluoride is treated at about 25 C. with fluosulfonic acid, the fluorinecontent is reduced more than 997 to give a propane fraction containingonly no harmful action on dry skin. .tothe touch and is without theintense blistering found that neitherhydrogen fluoride alone norsulfuric acid alone nor a mixture of hydrogen fluoride and sulfuric acidwill defluorinate to anything near this extent, that is, hydrogenfluoride alone or sulfuric acid alone had about 20% of thedefluorinating activity of fluosulfonic acid while a mixture of sulfuricacid and hydrogen fluoride waslittle more than 40% as effective asfluosulfonic acid.

After prolonged use, the fluosulfonic acid may be regenerated bydistillation but when only small percentages of fluorine are present inthe charging stock, the cheapness of the fluosulfonic acid may permit itto be discarded after it has become contaminated too much for furtheruse.

One method of preparing fluosulfonic acid, used .in the process of thisinvention, consists in treating fluorspar (CaFz) with fuming sulfuricacid (-60%-SO3) Fluosulfonic acid is a mobile liquid with a boilingpoint of 163 C. at 760 mm. pressure and has a faint pungent odor butsubstantially It feels greasy action of anhydrous hydrogen fluoride.

' According to the process of the present invention, hydrocarbonmaterial contaminated by organicfluorine compounds is freed from a sub-.stantial proportion of such organically combined fluorine by treatmentwith fluosulfonic acid at a temperature of from about 50." to about 150C.

and preferably at a temperatureof from about 0 to about 50 C. The process is carried out at atmospheric pressure or at a superatmosphericpressure sufficient to maintain the fluorine-containing hydrocarbon orhydrocarbon mixture in substantially liquidphase.

The treatment of the hydrocarbon or hydrocarbon mixture withfluosulfonic acid is effected use in treating an additional the latteris washed, dried, and distilled or otherwise treated to recover thedesired hydrocarbon or hydrocarbons substantially free fromfluorinecontaining compounds, while the used fluosulfonic acid isreturned to the reactor for further quantity of the hydrocarbon chargingstock.

Continuous treatment of a hydrocarbon containing organically combinedfluorine is effected by passing said hydrocarbon and a proportionedamount of fluosulfonic acid through a baiiied mixer orother suitabletype of contacting equipment in which the hydrocarbon and fluosulfonicacid are contactedat the aforementioned conditions of temperature andpressure for a time suflicient to effect the removal of substantiallyall of V the fluorine from the hydrocarbon material. Fromthis treatingequipment the mixture of hydrocarbon-material and fluosulfonic acid isdirected to a separator from which the hydrocarbon layer is removed andthenwashed, dried, and distilled or otherwise-treated to recover thedesired hydrocarbons substantially free from fluorine-containingcompounds. The used fluosulfonic acid is then withdrawn from theseparator and a portion of it is recycled to further use in treating anadditional quantity of the mentioned charging stock.

The following examples are given to show results obtained in theoperation of the process. but they are not to be considered to undulylimit the broadscope of the invention.

Example I Several. runs were made in each of which 51 grams of a propanefraction containing small amounts of ethyl fluoride was contacted with174 grams of fluosulfonic acid at 25 C. for 3 hours in a rotatable steelautoclave of 850 cc. capacity. After this treatment the rotation of theautoclave was stopped and the reaction mixture was permitted to stand at25 C. for 14 hours.

The fluorine content of the propane fraction charged in each of theseruns and the defluorination effect by the treatment with fluosulfonicacid are as follows:

Per cent by weight fluorine in propane (present g as ethyl fluoride)1.21 1.53

Weight per cent fluorine I in propane product 0.0013 0.0053 0.0010

Per cent defluorination of propane charged 99.9 99.7 99.5

Example II Charge, grams:

Propane 102 102 Hydrogen fluoride 106 Sulfuric acid, 96% 183 Weight percent fluorine in propane product 0.95 0.95 7 Per cent defluorination ofpropane charged 21 19 Example III A run similar to those referred to inExample II was made in which 102 grams of propane containing ethylfluoride (0.209% by weight fluorine) was contacted at 25 C. with 115grams of hydrogen fluoride and 27 grams of sulfuric acid of 96%concentration. The propane recovered from this treatment had a fluorinecontent of 0.12% by weight corresponding to 43% defluorination of thepropane charged.

The nature of the present invention and the type of results obtained inthe process are evident from the preceding specification and examples,although neither section should be construed to unduly limit the broadscope of the invention.

I claim as my invention:

1. A process for treating a saturated hydrocarbon material containing asan impurity a relatively small percentage of organically combinedfluorine to remove fluorine therefrom which comprises contacting saidhydrocarbon material with fluosulfonic acid'at defluorinating conditionsof temperature and pressure, and recovering the treated hydrocarbonmaterial.

2. A process for treating a paraffin hydrocarbon material containing asan impurity a relatively small percentage of an alkyl fluoride to remo efluorine therefrom which comprises contacting said hydrocarbon materialwith fluosulfonic acid at defluorinating conditions of temperature andpressure, and recovering the treated hydrocarbon material.

3. A process for treating a hydrocarbon material containing as animpurity a relatively small percentage of organically combined fluorineand produce'dby catalytic alkylation of an isoparafilnic hydrocarbonwith an oleflnic hydrocarbon in the presence of an active fluoridecatalyst which comprises. treating said hydrocarbon material withfluosulfonic acid at defluorinating conditions of temperature andpressure, and recovering the treated hydrocarbon material.

4. A process for treating a hydrocarbon material containing as animpurity a relatively small hydrocarbon with an olefinic hydrocarbon ofhigher molecular Weight than ethylene in the presence of a hydrogenfluoride catalyst which comprises treating said hydrocarbon materialwith fluosulfonic acid at defluorinating conditions of temperature andpressure, and recovering the treated hydrocarbon material.

5. A process for treating a paraffin hydrocarbon material containing asan impurity a relatively small percentage of organically combinedfluorine to remove fluorine therefrom which comprises contacting saidhydrocarbon material with fluosulfonic acid at a temperature of fromabout 50 to about 150 C.. and recovering the treated hydrocarbonmaterial.

6. A process for treating a paraffin hydrocarbon material containing asan impurity a relatively small percentage of organically combinedfluorine to remove fluorine therefrom which comprises contacting saidhydrocarbon material with fluosulfonic acid at a temperature offromabout 50 to about 150 C. and at a pressure suflicient to maintainthe hydrocarbon material in substantially liquid phase, and recoveringthe treated hydrocarbon material.

7. A process for treating a parafiin hydrocarbon material containing asan impurity a relatively small percentage of an alkyl fluoride to removefluorine therefrom which comprises contacting said hydrocarbon materialwith fluosulfonic acid at a temperature of from about 50 to about 150C., and recovering the treated hydrocarbon material. I

8. A process for treating a paraffin hydrocarbon material containing asan impurity a relatively small percentage of an alkyl fluoride to removefluorine therefrom which comprises contacting said hydrocarbon materialwith fluosulfonic acid at a temperature of from about -50 to about 150C. and at a pressure sufiicient to maintain the hydrocarbon material insubstanorganically combinedfluorine to remove fluorine 10. A process fortreating butane containing as an impurity a relatively small percentageof organically combined fluorine to remove fluorine therefrom whichcomprises contacting said butane withfiuosulfonic acid atde'fluorinating con.- ditions of temperature and pressure, andrecovering the treated butane.

11. A process for treating a normally liquid pare. afiinic hydrocarbonmixture containing as an as an impurity a relatively small percentage oforganically combined fluorine to remove fluorine therefrom whichcomprises contacting said propane with fluosulfonic acid at atemperature of from about -50 to about 150 C., and recovering thetreated propane.

13. A process for treating butane containing as an impurity a relativelysmall percentage of organically combined fluorine to remove fluorinetherefrom which comprises contacting said butane with fluosulfonic acidat a temperature of from about 50 to about 150 C., and recovering thetreated butane.

14. A process for treating a normally liquid paraflinic hydrocarbonmixture containing as anlmpurity a relatively small percentage oforganically combined fluorine to removefiuorine there-- from whichcomprisescontacting said normally,

liquid paraflinic hydrocarbon mixture with fluosulfonic acid at atemperature of from about to about C., and recovering the treatednormally liquid paraflinic hydrocarbon mixture.

15. The process of claim 9 further characterized in that said impuritycomprises ethyl fluoride.

16. The process of claim 12 further characterized in that said impuritycomprises ethyl fluoride.

CARL B. LINN.

I REFERENCES CITED The following references are of record in the file ofthis patent:

' UNITED STATES PATENTS Number Name Date 1,950,878 Burk Mar. 13-, 19342,320,629 Matuszak June 1,1943 2,341,567 Moriarty Feb. 15, 19442,391,149 Frey Dec. 18, 1945 2,412,726 Frey Dec. 1'7, 1946

